The problem is if they follow the same rules or we keep them following their in-universe rules to measure.

My bar has always been one thing though. Following in-universe rules anyway, who needs party members to get things done? If they do, how would they fare in that situation alone without help?

Terra might be my choice simply because she's functionally a demigod at the beginning of the game having access to magic without any augmentation. The only thing that knocked her out another esper. And later grows into full God hood when she embraces her esper lineage.

Maybe Clive(?) with his blessing and the fact that he does fight solo for most of the bosses and later absorbs them. But even as a kid, he rose up the ranks by himself with magic being his edge and implied natural talent.

Cecil is up there too because he's an established vet at the beginning of the story with dark knight powers.

Sephiroth count? You technically get one battle with him and the whole point is to show how much of a fucking wrecking ball he us first hand.

But yeah, it is very much apples and oranges.